LED based lighting systems in aircrafts are known which comprise one or more LEDs (Light Emitting Diodes) which are mounted on one or more printed circuit boards (PCB) together with a power supply and control circuit(s) and which are interconnected by conductive paths on the printed circuit board. LED technology offers a number of advantages. For example, besides being highly cost-effective and having a long lifetime, power consumption is significantly lower than in other lighting systems with bulbs or the like.
Performance of an LED regarding light emission is very sensitive to the LED junction temperature. Roughly speaking, it can be said that in most operating regions the lower the temperature, the better the LED performance. Typically, above a particular threshold temperature, the LED may be damaged, therefore in typical applications an LED junction is thermally connected to the PCB and then to a heat sink to keep the temperature as low as possible.
The problem of high temperatures is pertaining particularly to high power LEDs which have no (electrically isolated) thermal pad (such as a pad made of copper for good thermal conductivity), i.e. only have cathode and anode pads that are responsible for thermal transfer from the LED junction to the PCB. The situation is worse if the number of LEDs arranged in an array on a PCB is very close to each other.
FIG. 1 shows an exemplary LED array 100 arranged on a PCB according to a previous approach in which multiple LEDs (such as LEDs 101, 102, etc.) are arranged in an array, with their anodes and cathodes (not shown as they are below the respective LED housing) connected to conductor paths, such as shown at 103 and 104.
In such case, the surface area of the conductor paths to the respective cathodes and anodes is limited by the confined spacing between the LEDs of the array, which necessitates relatively thin or narrow electrical conductors or traces on the PCB. Hence the thermal transfer is limited which results in higher LED junction temperatures, which then results in reduced LED performance and efficiency, particularly reduced light emission.
Accordingly, it would be beneficial to provide an aircraft LED light unit that exhibits increased LED efficiency.